Redox-responsive self-healing materials formed from host-guest polymers.

Self-healing pH-sensitive poly[(methyl vinyl ether)-alt-(maleic acid)]-based supramolecular hydrogels formed by inclusion complexation between cyclodextrin and adamantane

The introduction of non-covalent bonds is effective for achieving self-healing properties because they can be controlled reversibly. One approach to introduce these bonds into supramolecular materials is use of host-guest interactions. This feature article summarizes the development of supramolecular materials constructed by non-covalent cross-linking through several approaches, such as host-guest interactions between host polymers and guest polymers, 1 : 2-type host-guest interactions, and host-guest interactions from the polymerization of host-guest inclusion complexes. Host-guest interactions show self-healing functions while also enabling stimuli-responsiveness (redox, pH, and temperature). The self-healing function of supramolecular materials is achieved by stress dispersion arising from host-guest interactions when stress is applied. Reversible bonds based on host-guest interactions have tremendous potential to expand the variety of functional materials.

The host-guest interaction as noncovalent bonds can make polymeric materials tough and flexible based on the reversibility property, which is a promising approach to extend the lifetime of polymeric materials. Supramolecular materials with cyclodextrin and adamantane are prepared by mixing host polymers and guest polymers by planetary ball milling. The toughness of the supramolecular materials prepared by ball milling is approximately 2 to 5 times higher than that of supramolecular materials prepared by casting, which is the conventional method. The materials maintain their mechanical properties during repeated ball milling treatments. They are also applicable as self-healable bulk materials and coatings, and they retain the transparency of the substrate. Moreover, fractured pieces of the materials can be re-adhered within 10 min. Dynamic mechanical analysis, thermal property measurements, small-angle X-ray scattering, and microscopy observations reveal these behaviors in detail. Scars formed on the coating disappear within a few seconds at 60°C. At the same time, the coating shows scratch resistance due to its good mechanical properties. The ball milling method mixes the host polymer and guest polymer at the nano level to achieve the self-healing and recycling properties.

Supramolecular hydrogelation via host-guest anion recognition: Lamellar hydrogel materials for the release of cationic cargo

Host–guest interaction and structural ordering in polymeric nanoassemblies: Influence of molecular design

Living systems, including human beings, animals, and plants, display the power to self-heal spontaneously after being damaged. The self-healing is usually selective, which means that the healing efficiency is related to the spatial distribution of dynamic interfacial interactions of the two rupturing surfaces. Current artificial systems use noncovalent interactions or dynamic covalent bonds to prepare self-healing materials. However, they can only show nonselective self-healing due to their homogeneous internal structures. Herein, we report the construction of a composite hydrogel Gel- C consisting of three different self-healing hydrogels (Gel- Y, Gel- G, and Gel- O) through the use of classic bilayer hydrogel technology. When the composite hydrogel was cut into two pieces, the relative orientation of the parts was rotated through different angles to study the differences in self-healing. Owing to the heterogeneous internal structure of the composite hydrogel and the recognition specificity of each included hydrogel, the interfacial dynamic interactions distribution of the two rupturing surfaces is diverse. The results of tensile tests demonstrated that these rotated samples exhibited different self-healing efficiencies. This system realized the transformation of artificial materials from nonselective self-healing to selective self-healing, providing inspiration for the development of novel biological materials and engineering materials.

Reinforcing DNA Supramolecular Hydrogel with Polymeric Multiple-Unit Linker

Biopolymer-based supramolecular hydrogels cross-linked by host–guest interactions are usually mechanically weak as shown in “inverted vials” instead of freestanding 3D constructs. Herein, we describe a novel host–guest macromer (HGM) approach for preparation of biopolymer-based freestanding supramolecular hydrogels. Host–guest macromers are formed by molecular self-assembly between adamantane-functionalized hyaluronic acid (ADxHA) guest polymers and monoacrylated β-cyclodextrins (mono-Ac-βCD) host monomers. Supramolecular hydrogels are readily prepared by UV-induced polymerization of the preassembled host–guest macromers. Such hydrogels are soely cross-linked by in situ formed multivalent host–guest nanoclusters and show significantly reinforced mechanical properties yet still retain desirable supramolecular features. They can self-heal and be remolded into freestanding 3D constructs which afford effective protection on the encapsulated stem cells during the compression remolding, making them promising ca...

Photo-responsive supramolecular hyaluronic acid hydrogels for accelerated wound healing

Synthesis and characterization of self-healable supramolecular hydrogel based on carboxymethyl cellulose for biomedical applications

Water‐cut control is critical to efficient reservoir development. In this investigation, a host‐guest inclusion polymer gels system with self‐assembly features was constructed stemming from the host‐guest recognition mechanism. Subsequently, the elements affecting polymer viscosity were discussed. Eventually, the injectivity and plugging performance of the host‐guest inclusion system were measured by core displacement tests. The results indicated that the optimum synthesis temperature of the host polymer and guest polymer were 30 °C and 40 °C, separately, and the optimum total monomer content should be 20 wt%. The polymer system had excellent thickening properties and shearing resistance resulting from host‐guest inclusion interaction and physical hydrophobic association. Meanwhile, it had better plugging performance than host polymer or guest polymer alone. This profile control agent system provides a novel method for settling deep profile control in oilfields.

Supramolecular hydrogels have a unique crosslinked structure because of utilizing supramolecular binding motifs including dynamic covalent bonds (Schiff-base linkage, Diels–Alder reaction, disulfide exchange reaction, and boronic ester formation) and noncovalent bonds (hydrogen bonding, electrostatic interactions, hydrophobic interactions, and host–guest interactions). When the supramolecular binding motifs can act as dynamic crosslinks, the supramolecular hydrogels can have a function of self-healing that is defined as healing damages, restoring itself to normality intrinsically. By a combination of double network structure or slide-ring structure such as polyrotaxanes with the supramolecular binding motifs, the supramolecular self-healing hydrogels become tough, which is capable of long-term use for various applications. These supramolecular self-healing hydrogels have been developed for biomedical and industrial applications, including tissue engineering, corrosion, and biofouling.

Supramolecular hydrogels based on host-guest interactions have drawn considerable attention due to their unique properties and promising applications. However, it is still a great challenge to construct supramolecular hydrogels that simultaneously achieve mechanical strength, processability, and biocompatibility. Herein, we present a rational design of a "supramolecular crosslinker" approach to fabricate a new host-guest hydrogel with super-stretchability, self-healing, and injectable properties and excellent biocompatibility. The star-shaped supramolecular crosslinker is formed by the host-guest interactions between octa-cyclodextrin polyhedral oligomeric silsesquioxane (OCDPOSS) and acrylamide-modified adamantane (Ad-AAm). Supramolecular hydrogels can be briefly prepared by UV-initiated copolymerization of acrylamide and supramolecular crosslinkers. Supramolecular hydrogels present impressive mechanical properties due to rigid POSS as the core of the supramolecular crosslinker. Moreover, multivalent host-guest interactions improve the ductility, rapid self-healing and injectable ability of these hydrogels. Simultaneously, these supramolecular hydrogels possess good biocompatibility and can be utilized as carriers for the sustained release of hydrophobic drugs. Thus, such supramolecular hydrogels will have potential applications for tissue engineering and drug delivery systems.

Self-healable tough supramolecular hydrogels crosslinked by poly-cyclodextrin through host-guest interaction

In recent decades, in vitro three-dimensional (3D) cell culture has been rapidly developed and widely used in many biomedical fields. Based on this background, a kind of self-assembled supramolecular hybrid hydrogel materials based on host-guest interaction of β-cyclodextrin (βCD) and adamantane (Ad) is designed for 3D cell culture. First, βCD is grafted to poly(methyl vinyl ether-alt-maleic acid) (PMM) to obtain the host polymers of βCD-grafted-PMM (PMM-βCD). Second, the guest polymers of poly(acrylamide-co-N-adamantyl acrylamide) (PAAm-Ad) are synthesized through free-radical copolymerization of acrylamide and N-adamantyl acrylamide. Finally, the self-assembled supramolecular hybrid hydrogels of PMM-βCD/PAAm-Ad are formed by simply mixing the aqueous solution of host and guest polymers with a total concentration of 3.3% (w/v) and a βCD/Ad molar ratio of 1:1. The main cross-linking interactions come from the host-guest interaction of βCD/Ad as well as hydrogen-bonding interaction of carboxyl/amide groups. The prepared hydrogels with good cytocompatibility have been successfully used as 3D cell culture scaffold for SKOV3, HUVEC, and L929 cells culture. Thus, this work provides a way and biomaterial for the preparation of a functionalized 3D cell culture scaffold, which lays an experimental and theoretical basis for cell follow-up research.